This invention relates to blade elements used in compressor and turbine rotors. More particularly, the invention relates to a blade assembly that can be used to replace damaged blades in the field.
An axial flow compressor comprises a rotor made up of a plurality of wheels attached to a shaft, the wheels providing the compression stages of the compressor. Each compressor wheel is typically an annular disk with a plurality of blade elements attached to its outer rim. The blade elements typically have a blade portion with an airfoil-shaped cross-section and an arrangement for attaching the blade element to the wheel. The attachment arrangement is typically a dovetail-shaped base configured for placement in a correspondingly shaped groove or slot in the wheel.
Compressor rotors rotate at high speeds to compress large volumes of gas. Unfortunately, the gas entering the intake of the compressor may sometimes include solid matter. The compressor blades are therefore subject to occasional damage due to high speed collision with solid particles. Such foreign object damage (FOD) can be severe enough that the damaged blade must be machined or replaced. The components of early (i.e., low pressure) stage compressor wheels/blades are often large enough that damaged blades may be machined in place. Later stage blades, however, typically require removal. Depending on the configuration of the blade attachment arrangement, this can require removal and disassembly of the entire wheel.
The present invention provides a replacement blade assembly that allows the replacement of damaged blade elements without removal and disassembly of the rotor.
Accordingly, the present invention provides a blade assembly for installation in a rotor wheel slot having a slot neck in communication with a slot base cavity defined by first and second slot flank walls and a slot floor. The blade assembly comprises a blade element having an airfoil portion and a base portion configured for insertion into the rotor wheel slot through the slot neck. The blade assembly also comprises at least one filler piece configured for insertion into the rotor wheel slot through the slot neck. The at least one filler piece is also configured for positioning intermediate the base portion and the first slot flank wall to secure the base portion within the rotor wheel slot.
The base portion of the blade element of a blade assembly according to the invention may include a base dovetail having first and second dovetail flank surfaces and a dovetail bottom surface. The blade assembly may comprise a first filler piece configured to be positionable with at least a portion of the first filler piece disposed intermediate the first dovetail flank surface and the first slot flank wall. The blade assembly may further comprise a second filler piece configured so that at least a portion of the second filler piece is disposable intermediate the second dovetail flank surface and the second slot flank wall. The at least a portion of the first filler piece may include a first engaging surface adapted for engaging the first slot flank wall and a second engaging surface adapted for engaging the first dovetail flank surface. The at least a portion of the second filler piece may include a third engaging surface adapted for engaging the second slot flank wall and a fourth engaging surface adapted for engaging the second dovetail flank surface. The first and second filler pieces may each include a bottom member configured so that the bottom member is disposed intermediate the dovetail bottom surface and the slot floor. At least a portion of the bottom member may be configured to engage the dovetail bottom surface and the slot floor.
In an embodiment of the invention, the base portion of the blade element may include a base dovetail having first and second dovetail flank surfaces and a dovetail bottom surface. The blade assembly may comprise a first plurality of filler pieces sized and configured to be positionable with at least a portion of each of the first plurality of filler pieces disposed intermediate the first dovetail flank surface and the first slot flank wall. A second plurality of filler pieces may be sized and configured to be positionable with at least a portion of each of the second plurality of filler pieces disposed intermediate the second dovetail flank surface and the second slot flank wall. The at least a portion of each of the first plurality of filler pieces may include a first engaging surface adapted for engaging the first slot flank wall and a second engaging surface adapted for engaging the first dovetail flank surface. The at least a portion of each of the second plurality of filler pieces may include a third engaging surface adapted for engaging the second slot flank wall and a fourth engaging surface adapted for engaging the second dovetail flank surface. Each of the first and second plurality of filler pieces may include a bottom member configured so that the bottom member is disposed intermediate the dovetail bottom surface and the slot floor. The at least a portion of the bottom member may be configured to engage the dovetail bottom surface and the slot floor.
Embodiments of the blade assembly of the invention may comprise a spacer configured for insertion into the rotor wheel slot through the slot neck. The spacer may be further configured for positioning within the rotor wheel slot in abutment with the base portion of the blade element. The spacer may have a spacer dovetail with first and second spacer flank surfaces configured for engagement with the first and second slot flank walls. The blade assembly may further comprise means for securing the spacer in place within the rotor wheel slot. The means for securing may include a threaded fastener having proximal and distal ends. The threaded fastener may be configured for insertion through a corresponding threaded passage in the spacer so that the distal end contacts the floor of the slot dovetail.
An embodiment of the invention provides a blade assembly for installation on a rotor wheel having a blade slot formed in a circumferential rim thereof, the blade slot having a substantially constant cross-section with a slot neck in communication with a slot base cavity having first and second flank surfaces and a floor. The blade assembly comprises a blade element having an airfoil portion and a base portion. The base portion has first and second base flank surfaces and is configured for insertion into the blade slot through the slot neck. The blade assembly further comprises a first filler piece configured to be positionable with at least a portion of the first filler piece disposed intermediate the first base flank surface and the first slot flank wall. The blade assembly also comprises a second filler piece configured so that at least a portion of the second filler piece is disposable intermediate the second base flank surface and the second slot flank wall. At least a portion of the first filler piece may include a first engaging surface adapted for engaging the first slot flank wall and a second engaging surface adapted for engaging the first base flank surface. At least a portion of the second filler piece may include a third engaging surface adapted for engaging the second slot flank wall and a fourth engaging surface adapted for engaging the second base flank surface.
One aspect of the invention provides a blade assembly for installation on a rotor wheel having a blade slot formed in a circumferential rim thereof, the blade slot having a substantially constant cross-section with a slot neck in communication with a dovetail-shaped slot base cavity defined by first and second flank surfaces and a floor. The blade assembly comprises a blade element having an airfoil portion and elongate base portion including a base dovetail having first and second dovetail flank surfaces and a dovetail bottom surface. The base portion is configured for insertion into the blade slot through the slot neck. The blade assembly also comprises a first plurality of filler pieces sized and configured to be positionable with at least a portion of each of the first plurality of filler pieces disposed intermediate the first dovetail flank surface and the first slot flank wall. The blade assembly further comprises a second plurality of filler pieces sized and configured to be positionable with at least a portion of each of the second plurality of filler pieces disposed intermediate the second dovetail flank surface and the second slot flank wall.
One aspect of the invention provides a method of replacing a blade element installed on a rotor wheel having a blade slot formed in a circumferential rim thereof. The blade slot has a substantially constant cross-section with a slot neck in communication with a slot base cavity having first and second slot flank walls and a slot floor. The blade element has an airfoil portion and a blade element base portion disposed within the blade slot. The method comprises removing the blade element from the blade slot and providing a replacement blade element having a replacement blade airfoil portion and a replacement blade element base portion. The replacement blade element base portion is configured for insertion into the blade slot through the slot neck. The replacement blade element base portion also has opposing first and second base ends. The method further comprises inserting the replacement blade element base portion into the blade slot through the slot neck. The method still further comprises providing at least one filler piece configured for insertion into the blade slot through the slot neck and for positioning intermediate the replacement blade element base portion and the first slot flank wall for securing the replacement blade element base portion within the blade slot. A first one of the at least one filler piece is inserted through the slot neck into the blade slot adjacent one of the first and second base ends. The first one of the at least one filler piece is then positioned against the first slot flank wall. The first one of the at least one filler piece is then slid along the first slot flank wall to a position wherein the first one of the at least one filler piece is disposed intermediate the replacement blade element base portion and the first slot flank wall.
A method of replacing a blade element according to the invention may comprise inserting a second one of the at least one filler piece through the slot neck into the blade slot adjacent one of the first and second base ends. The second one of the at least one filler piece is then positioned against the second slot flank wall. The method may further comprise sliding the second one of the at least one filler piece along the second slot flank wall to a position wherein the second one of the at least one filler piece is disposed intermediate the replacement blade element base portion and the first slot flank wall.
A method of replacing a blade element according to the invention may comprise providing a first spacer configured for insertion into the blade slot through the slot neck. The first spacer is further configured for positioning within the blade slot in abutment with the base portion of the blade element. The spacer has a spacer base with first and second spacer flank surfaces configured for engagement with the first and second slot flank walls and a first spacer abutment surface configured for engaging the first base end. The method may further comprise providing means for securing the first spacer in place within the blade slot. The method may also comprise inserting the first spacer through the slot neck into the blade slot adjacent the first base end. The first spacer is then positioned within the blade slot so that the first spacer flank surface engages the first slot flank wall, the second spacer flank engages the second slot flank wall, and the first spacer abutment surface engages the first base end. The first spacer is then secured in position using the means for securing the first spacer. The means for securing the first spacer may include a threaded fastener disposed through a corresponding threaded passage in the first spacer so that rotation of the threaded fastener causes an end of the threaded fastener to engage the slot floor and force the spacer radially outward. The method may further comprise the step of machining a depression in the slot floor to provide a seat for the threaded fastener end.
A method of replacing a blade element according to the invention may comprise providing a second spacer configured for insertion into the blade slot through the slot neck and for positioning within the blade slot in abutment with the base portion of the blade element. The second spacer has a second spacer base with third and fourth spacer flank surfaces configured for engagement with the first and second slot flank walls and a second spacer abutment surface configured for engaging the second base end. The method may further comprise providing means for securing the second spacer in place within the blade slot. The second spacer is inserted through the slot neck into the blade slot adjacent the second base end. The second spacer is then positioned within the blade slot so that the third spacer flank surface engages the first slot flank wall, the fourth spacer flank engages the second slot flank wall, and the second spacer abutment surface engages the second base end. The second spacer is secured in position using the means for securing the second spacer.
The step of removing the blade element from the blade slot in a method of replacing a blade element according to the invention may include removing the airfoil portion of the blade element, grinding out a central portion of the blade element base portion through the slot neck to leave two lateral portions of the blade element base portion in the slot base cavity, and removing the two lateral portions of the blade element base portion from the blade slot through the slot neck.
Other objects and advantages of the invention will be apparent to one of ordinary skill in the art upon reviewing the detailed description of the invention.